P-Phenylenediamine

p-Phenylenediamine
IUPAC name	1,4-diaminobenzene
Identifiers
CAS number	[106-50-3]
SMILES	Nc1ccc(N)cc1
InChI	1/C6H8N2/c7-5-1-2-6 (8)4-3-5/h1-4H,7-8H2
Properties
Molecular formula	C6H8N2
Molar mass	108.1
Appearance	Tan solid
Melting point	143-145 °C
Boiling point	267 °C, 540 K, 513 °F
Hazards
R-phrases	R23 R24 R25 R36 R37 R38 R40 R42 R43
S-phrases	S26 S36 S37 S39
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references

p-Phenylenediamine (PPD), also called paraphenylenediamine, 1,4-diaminobenzene or 1,4-phenylenediamine is an aromatic amine used as a component of engineering polymers and composites, aramid fibers, hair dyes, rubber chemicals, textile dyes, and pigments. PPD is selected because of its high temperature stability, high strength, and chemical and electrical resistance. However, it may cause allergic reactions, which makes it a controversial chemical to be included in hair dyes.

Uses

This product is added to real henna to create so called "Black Henna," which, in many cases, causes allergic reaction, and can cause scarring in some people. PPD should never be applied directly to the skin in its pure form or mixed with anything else.^[1]

This compound is used in almost every hair dye on the market, regardless of brand. The darker the colour, usually, the higher the concentrations. Some of the so-called "natural" and "herbal" hair colours, while ammonia-free, contain PPD. Some products sold as henna have PPD added, particularly "black henna." Using body art-quality (BAQ) pure henna, or indigo, is the only way to avoid PPD in hair dye.

PPD is used in the manufacture of aramid plastics and fibers such as Kevlar as well as substituted p-phenylenediamines that are used as antiozonants in rubber.

Safety

When tested by the United States Environmental Protection Agency, the EPA reported that in rats and mice chronically exposed to PPD in their diet, it simply depressed body weights, but there were no other clinical signs of toxicity, as were observed in several studies.^[2] There have been thirty-one published articles investigating a causal association between PPD and cancer between the years 1992-2005. Associations between personal hair dye use and non-Hodgkin's lymphoma, multiple myeloma, acute leukemia, and bladder cancer^[3] were observed in at least one well-designed study with detailed exposure assessment, but were not consistently observed across studies. However, the EPA has not classified PPD as a carcinogen. Therefore, no warnings of toxicity have been printed on boxes of hair dye.

The CDC lists PPD as being a contact allergen. Exposure routes are through inhalation, skin absorption, ingestion, and skin and/or eye contact; symptoms of exposure include throat irritation (pharynx and larynx), bronchial asthma, and sensitization dermatitis.^[4][5] Sensitization is a lifelong issue, which may lead to active sensitization to products including, but not limited to:

• Black clothing
• Printer ink
• Facsimile ink
• Hair dye
• Fur dye
• Leather dye
• Photographic products.

One maker of this product states explicitly that PPD should not be used directly on the skin^[6]

It was voted Allergen of the Year in 2006 by the American Contact Dermatitis Society.

Misconception

Some misinformation twists have led to PPDs being described as a black mineral from the banks of the River Nile^{[citation needed]}. This gives PPD an undeserved impression that it is both natural and exotic, though most PPD is synthetic.

References

External links

• Du Pont technical data sheet and sales policy for p-Phenylenediamine (PPD)